This invention relates to a titrating device wherein electrolytic current is supplied continuously and controlled to titrate the quantity of electricity so as to automatically perform qualitative analysis of the moisture or electrolizable substances contained in a sample.
According to a prior art coulometric titrating device an electrolytic current of a definite value is on-off controlled and the interval of current conduction is integrated for measuring the electric quantity required for the electrolysis until an end point is reached. However, such prior art device has the following disadvantages.
A. It is necessary to pass current of a constant value from the beginning to the end of the measurement. Thus, it is necessary to interrupt large electrolytic current near the end point so that it is impossible to perform accurate analysis by finely adjusting the current. Consequently, the accuracy of the measurement is limited. Especially, the accuracy of the analysis of small quantities is low.
B. As it is necessary to maintain the accuracy of the analysis in a prescribed range it is not permitted to increase the electrolytic current beyond a certain value with the result that analysis of large quantities requires long times.
C. Since the integration of the electric quantity is performed by a time integration of a constant current, it is usually necessary to maintain the current at a constant value and the range of measurement is limited to a narrow one in view of the accuracy and time of analysis.
D. Since a constant current is used, when the resistivity of the solution is increased beyond a certain value, the electrolytic current of a set value will not flow thus disenabling the measurement. For this reason, there is a lower limit for the electric conductivity of the solution to be analyzed.
e. When the blank caused by such factors as a sample, a reagent or an electrolytic reaction cell increases, the end point becomes unstable, thus causing measuring errors, and in an extreme case it is impossible to measure.